Time course, factors related to, and prognostic impact of venoarterial extracorporeal membrane flow in cardiogenic shock.

Abstract

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is currently one of the most used devices in refractory cardiogenic shock. However, there is a lack of evidence on how to set the 'optimal' flow. We aimed to describe the evolution of VA-ECMO flows in a cardiogenic shock population and determine the risk factors of 'high-ECMO flow'. A 7year database of patients supported with VA-ECMO was used. Based on the median flow during the first 48h of the VA-ECMO run, patients were classified as 'high-flow' or 'low-flow', respectively, when median ECMO flow was ≥3.6 or <3.6L/min. Outcomes included rates of ventilator-associated pneumonia, ECMO-related complications, days on ECMO, days on mechanical ventilation, intensive care unit and hospitalization lengths of stay, and in-hospital and 60day mortality. Risk factors of high-ECMO flow were assessed using univariate and multivariate cox regression. The study population included 209 patients on VA-ECMO, median age was 51 (40-59) years, and 78% were males. The most frequent aetiology leading to cardiogenic shock was end-stage dilated cardiomyopathy (57%), followed by acute myocardial infarction (23%) and fulminant myocarditis (17%). Among the 209 patients, 105 (50%) were classified as 'high-flow'. This group had a higher rate of ischaemic aetiology (16% vs. 30%, P=0.023) and was sicker at admission, in terms of worse Simplified Acute Physiology Score II score [40 (26-58) vs. 56 (42-74), P<0.001], higher lactate [3.6 (2.2-5.8) mmol/L vs. 5.2 (3-9.7) mmol/L, P<0.001], and higher aspartate aminotransferase [97 (41-375) U/L vs. 309 (85-939) U/L, P<0.001], among others. The 'low-flow' group had less ventilator-associated pneumonia (40% vs. 59%, P=0.007) and less days on mechanical ventilation [4 (1.5-7.5) vs. 6 (3-12) days, P=0.009]. No differences were found in lengths of stay or survival according to the ECMO flow. The multivariate analysis showed that risk factors independently associated with 'high-flow' were mechanical ventilation at cannulation [odds ratio (OR) 3.9, 95% confidence interval (CI) 2.1-7.1] and pre-ECMO lactate (OR 1.1, 95% CI 1.0-1.2). In patients with refractory cardiogenic shock supported with VA-ECMO, sicker patients had higher support since early phases, presenting thereafter higher rates of ventilator-associated pneumonia but similar survival compared with patients with lower flows.